Understanding Converging Lenses: Question on Image Size

  • Thread starter Thread starter dioprem
  • Start date Start date
  • Tags Tags
    Converging Lenses
Click For Summary

Homework Help Overview

The discussion revolves around understanding the behavior of converging lenses, specifically regarding the size of the image formed compared to the object. The original poster presents a scenario involving rays of light and their interaction with a lens, questioning why the image produced is the same size as the object.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand the reasoning behind the image size being equal to the object size, given the constraints of drawing only two rays from a specific point. Some participants suggest considering additional rays or symmetry in the setup, while others clarify the conditions under which the image size remains unchanged.

Discussion Status

Participants are exploring various interpretations of the problem, with some providing insights into the symmetry of light rays and their implications for image size. There is acknowledgment of the constraints imposed by the problem, and guidance has been offered regarding the reasoning behind the image formation.

Contextual Notes

The original poster is limited to drawing only two rays from a specified point on the object, which raises questions about the completeness of their analysis and understanding of the lens behavior.

dioprem
Messages
11
Reaction score
0

Homework Statement



This is the given question. The blue rays represent the solution.
http://img16.imageshack.us/img16/7237/lenstq.jpg



Homework Equations


None.


The Attempt at a Solution



The blue rays are essentially my solutions, but only up to the point where the rays are reflected off the mirror. The rays after hitting the lens after that are from my teacher. Once they hit the lens, I know the 2 rays need to converge at a point along the focal plane, since the rays are parallel. What I want to know is why is the image the same size as the object?
 
Last edited by a moderator:
Physics news on Phys.org
Try drawing rays from other points on the needle such a point Y.
 
CWatters is right. Rays from X and Y are parallel.
 
@CWatters The problem is the solution requires me to only draw to rays from point X. So I cannot draw addition rays from point X or any other rays from any other point of the needle. Only 2 rays from X are allowed. So I don't understand why the image is the same size as the object.
 
Consider a third ray from X which hits M right in the middle (you don't have to draw it). It is symmetric around the optical axis, and it has to hit the same point as the other two rays. Y is projected on itself. Therefore, the image of (XY) has the same size as (XY).
 
magnification = - image distance/object distance
 
Thank you mfb and Basic_Physics. Answered my question!
 

Similar threads

Analyzing this 2-lens optical system
  • · Replies 5 ·
Replies
5
Views
2K
Problem on thermal radiation and lenses
  • · Replies 3 ·
Replies
3
Views
2K
Understanding Two Convex Lenses: Ray Diagram and Focal Lengths
  • · Replies 3 ·
Replies
3
Views
3K
Mirror placed horizontally between two half convex lenses
  • · Replies 11 ·
Replies
11
Views
2K
Focal length of the eyepiece lens in a compound microscope
  • · Replies 7 ·
Replies
7
Views
2K
Convergent lenses and calculating image position
  • · Replies 2 ·
Replies
2
Views
2K
Algebraic Explanation of Image Formation in Convex Lenses
  • · Replies 1 ·
Replies
1
Views
1K
Multiple Lens System(Objectless and Parallel Rays)
  • · Replies 2 ·
Replies
2
Views
2K
Emergent light produced by two lenses
  • · Replies 15 ·
Replies
15
Views
2K
Inserting thick lenses into a thin lens system and deducing values
  • · Replies 1 ·
Replies
1
Views
2K